code: def _fil_megmag(raw_test, raw_mat):
      """Test the magnetometer channels."""
      test_inds = pick_types(
          raw_test.info, meg="mag", ref_meg=False, exclude="bads"
      )
      test_list = list(raw_test.info["ch_names"][i] for i in test_inds)
      mat_list = raw_mat["label"]
      mat_inds = _match_str(test_list, mat_list)
  
      assert len(mat_inds) == len(
          test_inds
      ), "Number of magnetometer channels in RAW does not match .mat file!"
  
      a = raw_test._data[test_inds, :]
      b = raw_mat["trial"][mat_inds, :] * 1e-15  # fT to T
  
      assert_array_equal(a, b)
  
file_path: mne-python/mne/io/fil/tests/test_fil.py
imports: import shutil
  from os import remove
  import pytest
  import scipy.io
  from numpy import array, empty, isnan
  from numpy.testing import assert_array_almost_equal, assert_array_equal
  from mne import pick_types
  from mne.datasets import testing
  from mne.io import read_raw_fil
  from mne.io.fil.sensors import _get_pos_units
label_desc: Use image node_id 4 for calling a global function with example usage: _fil_megmag(raw_test, raw_mat) without return types